[SGVLUG] [OT]Hybrids and trains (was fuel prices and the dollar)

[David Lawyer]

On Wed, May 14, 2008 at 11:01:44AM -0700, Rae Yip wrote:
> Don't forget regenerative braking; this is a big win for hybrid and
> electric vehicles because it saves wear and tear on the brake pads as
> well as improving mileage.
> 
> So even if the Prius loses 1/3 of the energy it stores in the
> batteries, much of that energy would simply have been discarded in a
> regular car - 100% loss!
Not so.  In a regular car you would coast a bit before applying the
brakes, even if you "coasted" in high gear with an AT.  Such coasting
is not as good as in neutral but it will save energy.  It can the
shown mathematically that even if you have regenerative braking, it's
optimal to coast a ways before applying the regenerative brakes since
coasting recovers 100% of the energy.
> 
> Naturally, you don't something for nothing. As people have said,
> there's added weight. But I doubt the auto makers would add a
> component that wasn't a net gain, and the real world data bears it
> out.
> 
> In stop-and-go traffic (is there any other sort in LA?), I'm fairly
> certain hybrid vehicles are more efficient, no matter how well you
> follow your car's fuel consumption map.

It may depend on just how stop-and-go it is.   If cars just slow down
slowly to a stop, one can get a fair amount of coasting in.
			David Lawyer